Bit and block assembly

ABSTRACT

A bit and block assembly in which the bit includes an elongate shank that is rotatively mounted in a block bore extending through the block, the bit shank being provided with an end extending through and beyond the mounting bore and laterally clear of the block. A bit head includes means adapted to strike a wall to turn the bit upon picking of the wall by the head. A locking means is carried by a lateral block portion that is spaced from the shank end, the locking means engaging the shank end to preclude unintentional withdrawal of the shank from the bore, yet enable turning of the shank, the lateral block portion protecting the locking means while the lateral space peripherally about the shank end enables cuttings to move through the bore and out of the block and to fall free axially of the shank end. In one embodiment, the block is provided with an open end counterbore larger than and communicating with the said bore. The shank end, including a peripheral groove adapted to receive a locking element, extends into the counterbore, such counterbore providing the peripheral lateral space about the shank end and groove. The shank can be provided with a plurality of circumferentially spaced, longitudinal grooves extending from substantially the head to the shank end outside of the mounting bore for the passage of material axially along the shank out of the block. In another embodiment, the bit shank includes a tapered end that is provided with the peripheral groove, the tapered shank end and groove being laterally spaced from the block defining the bore to provide for the free passage of material through the bore and out of the block.

limited States Patent Elders [4 1 Mar. 2%, 11972 [54] BIT AND BLOCK ASSEMBLY [72] Inventor: Gerald W. Elders,

, Christopher, Ill. 62822 [22] Filed: Mar. 2, 1970 [21] Appl.No.: 15,768

Related US. Application Data [63] Continuation-in-part of Ser. No. 498,639, Oct. 20,

10 Hillcrest,

Primary Examiner-Ernest R. Purser Attorney-Cohn and Powell [57 ABSTRACT A bit and block assembly in which the bit includes an elongate shank that is rotatively mounted in a block bore extending through the block, the bit shank being provided with an end extending through and beyond the mounting bore and laterally clear of the block. A bit head includes means adapted to strike a wall to turn the bit upon picking of the wall by the head. A locking means is carried by a lateral block portion that is spaced from the shank end, the locking means engaging the shank end to preclude unintentional withdrawal of the shank from the bore, yet enable turning of the shank, the lateral block portion protecting the locking means while the lateral space peripherally about the shank end enables cuttings to move through the bore and out of the block and to fall free axially of the shank end.

In one embodiment, the block is provided with an open end counterbore larger than and communicating with the said bore. The shank end, including a peripheral groove adapted to receive a locking element, extends into the counterbore, such counterbore providing the peripheral lateral space about the shank end and groove. The shank can be provided with a plurality of circumferentially spaced, longitudinal grooves extending from substantially the head to the shank end outside of the mounting bore for the passage of material axially along the shank out of the block.

In another embodiment, the bit shank includes a taperedend that is provided .with the peripheral groove, the tapered shank end and groove being laterally spaced from the block defining the bore to provide for the free passage of material through the bore and out of the block.

11 Claims, 6 Drawing Figures CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of copending US. application, Ser. No. 498,639, filed Oct. 20, 1965 and entitled Self-Sharpening Bit and Mounting Therefore and now abandoned.

BACKGROUND OF THE INVENTION This invention relates generally to improvements in a bit and mounting therefore, more particularly to an improved structural relationship between the bit and block that permits for the free passage of cuttings and other foreign material through the block bore and out of the block while permitting a point-attack bit to turn in the mounting to provide the selfsharpening action resulting in longer bit wear and life.

In the heretofore conventional construction, a bit having a cone-shaped, point-attack bit head has its shank fixed in the mounting block in a manner such as would prevent rotation of the shank. With this type of mounting, the cone-shaped bit head was worn severely on one side as the head bit into and scraped the mine wall. As a result, the bit required frequent replacement. Moreover, the cuttings and dust have the tendency to move down along the bit shank and pack into the bore between the shank and block, such packing action creat ing a blockage and a binding action on the bit shank that would have prevented the bit from rotating even if the shank were mounted in such block for rotation.

SUMMARY OF THE INVENTION A point-attack bit of the present bit and block assembly will turn automatically as the bit picks a wall so that wear is distributed substantially evenly over the periphery of the bit head, thereby creating a self-sharpening action. This self-sharpening bit includes a shank, a tapered head integral with the shank, and means on the tapered shank for striking the wall to turn the bit upon picking of the wall by the tapered head.

The block is provided with a substantially cylindrical bore, and the point-attack bit of the type mentioned previously, has its elongate shank rotatively mounted in the block bore, the bit shank having an end that extends through and beyond the mounting bore and is located laterally clear of the block. A locking means is carried by a lateral block portion spaced from the shank end, the locking means engaging the shank end to preclude unintentional withdrawal of the shank from the bore, yet enable turning of the shank. The lateral block portion protects the locking means while the lateral space peripheral about the shank end enables cuttings to move through the bore and out of the block and to fall free axially of the shank end. This structural arrangement prevents blockage of the bore and precludes the shank from being bound into the block and thereby assures free turning movement of the shank at all times.

In one embodiment, the block is provided with a recess into which the shank end, including the peripheral groove formed in the shank end in which the locking element rides during rotation of the shank, extends. The recess provides the space laterally about the shank end into which the cuttings can move from the bore and fall free axially along the shank end and out of the block. This recess can be an open end counterbore larger than and communicating with the bore.

The shank can be provided with a plurality of circumferentially spaced, longitudinal grooves extending from and substantially adjacent to the bit head to the shank end outside of the mounting bore for the passage of material axially along the shank and out of the block. To minimize the possibility of blockage of the longitudinal grooves, such grooves extend along the shank end and open into the peripheral locking groove.

In another embodiment of this assembly, the-bit shank in cludes a tapered end provided with the peripheral groove, the tapered shank end and groove being laterally spaced from the block defining the bore.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view, partly in cross section, of a bit and block assembly, illustrating the picking action of the bit;

FIG. 2 is a front end elevational view of the bit head shown in FIG. 1;

FIG. 3 is a fragmentary, cross-sectional view taken on line 3-3 of FIG. 1;

FIG. 4 is a fragmentary, side elevational view of the block showing the keyhole slot adapted to receive the resilient insert of the locking means;

FIG. 5 is a side elevational view, partly in cross section of a modified bit and block assembly, and

FIG. 6 is a fragmentary, cross sectional view of another modified bit and block assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS:

Referring now by characters of reference to the drawings, and first to the embodiment of FIGS. 1-4, it will be understood that the block 10 is provided with a substantially cylindrical bore 11 extending through the front block face 12 and the rear block face 13. The bore 11 is slightly flared at the front block face 12 to provide an upwardly divergent shoulder 14.

One embodiment of the point-attack bit is generally indicated by 15 and is shown in FIG. 1. This bit 15 includes an elongate shank 16 having a circular cross section. The shank 16 is rotatively mounted within the cylindrical block bore 11. A tapered head 17 is formed integrally and coaxially with the shank 16, the head 17 tapering toward the forward end of the bit. The larger end of the tapered head 17 is provided with a rearwardly facing, annular shoulder 20 engaging the front block face 12 about the block bore 11. The shank 16 includes an enlarged, outwardly diverging shank portion 21 integrally connected to the tapered head 17, the shank portion 21 engaging the annular bore shoulder 14.

Inserted in and attached to the smaller end of the tapered head 17 is a carbide cutting tip 22, the tip 22 being provided with a relatively sharp point. As is illustrated in FIG. 1, the tapered head 17 including the carbide tip 22 picks at the wall 23 in order to cut away a portion of such wall 23. The tapered head 17 enters the wall 23 with its smaller end foremost and with its longitudinal axis arranged at a slight angle to the surface of the wall in an intermittent picking action.

It will be understood that this bit and block assembly is utilized in a cutting machine that operates to move the bit head 17 point first into the wall 23 with the picking action described previously, and operates to move the bit head 17 continuously into, through and out of the wall 23 in a curved path for a complete picking and scraping action.

In the embodiment of FIG. 1, the tapered head 17 has a substantially conical configuration. A turning means generally referred to by 24 is provided on the tapered head 17, the tuming means 24 providing a cross section perpendicular to the shank and head axis which is a departure from a circular cross section. This turning means engages the wall 23 during picking action by the tapered head 17, the interengagement of the turning means 24 in wall 23 causes the head 17 and shank 16 to turn. In the bit species disclosed in FIG. 1, the turning means 24 includes ribs 25 on and extending spirally along the length of the tapered head 17. Specifically, in FIG. 1, the spiral ribs 25 extend laterally outward of the conical head 17. The number of spiral ribs 25 provided on the tapered head 17 can vary. A total of two such ribs 25 are shown in FIGS. 1 and 2. A turning motion is imparted to the tapered head 17 by the action of one or more such ribs 25 striking the wall 23, thereby causing the tapered head to be self-sharpened.

The bit 15 is assembled to the block 10 by inserting the bit shank 16 into the block bore 11 until the head shoulder 20 abuts the front block face 12. The block 10 is cut away at the rear to provide a recess 26 adjacent the block 10 into which the shank 28 extends. This shank end 28 is provided with a peripheral annular groove 27 that is spaced axially along the shank 16 from the rear block face 13.

The block includes a rearwardly extending block portion 30 partially defining the recess 26 and laterally spaced from the shank end 28. As is best seen in FIG. 4, the block portion 30 is provided with a rear opening keyhole slot 31. Each side of the block portion 30 is provided with a circular depression 32, the purpose and function of which will be apparent upon later description of parts.

The locking mechanism interconnecting the block 10 and bit includes a resilient insert 33 having enlarged end flanges that seat in the circular depressions 32. A locking pin 35 extends through and is carried by the rubber insert 33, one end of the pin 35 being provided with an integral plate 36 engaging the outer side of the rubber insert 33, while the inner end of the pin 35 is provided with an integral head 37 engaging the inside face of the rubber insert 33. The pin head 37, as is shown in FIGS. 1 and 3, is tapered to a point and has an arcuate length enabling the pin head 37 to ride in the annular groove 27 and engage the shank end 28 to preclude unintentional withdrawal of the shank 16 from the block bore 11, yet permitting turning of the shank 16 within the block bore 11 by the turning means 24 incident to picking action of the bit 15 into wall 23.

Upon insertion of the bit shank 15 into the block bore 11, the shank end 28 will laterally depress the pin head 37 into and against the resilient insert 33. When fully inserted, the resiliency of the insert 33 will snap the pin head 37 into the annular shank groove 27 to preclude unintentional withdrawal. To replace the bit 15, the bit shank 16 can be forcibly pushed, knocked or pried out of the block bore 11, the pin head 37 being rearwardly and/or laterally displaced as it rides outwardly on the rearmost sloping margin defining the annular shank groove 27 and on the shank end 28.

It may be possible for fine cuttings to work into the cylindrical bore 11 between the bit shank 16 and the block 10. Upon turning or twisting of the bit shank 16 while the bit head 17 is picking the wall 23, the cuttings will move down through the block bore 11 and be discharged out the bottom of the block 10, the cuttings falling freely into and out of the block recess 26 around the shank end 28.

Without the provision of the lateral recess peripherally about the shank end 28, it is necessary to provide greater tolerances between the bit shank and the block wall defining the bore in order to have any chance for the passage of cuttings and other material through the bore. As a result of these greater tolerances, the bit shank moves longitudinally axially in an in-and-out action that causes severe shock and pounding between the bit and block and between the bit shank and locking pin. In such structure, the shank groove is made larger than the locking pin on purpose to permit such in-andout movement. However with the present bit and block assembly, it is possible to hold the bit shank and bore tolerances considerably closer which reduces the in-and-out action of the bit and thereby minimizes the shock and pounding between the bit and block and between the bit shank and locking pin. It is also possible under these circumstances to make the connection between the shank groove and locking pin tighter which assists further in reducing shock and pounding conditions. These advantages can all be achieved while providing an efficient passage for cutting the material through the bore and out of the block and maintaining bit shank rotation.

To further assist in moving the cuttings and other material through the bore 11 and out of the block 10, the bit shank 16 can be provided with a plurality of circumferentially spaced, longitudinal grooves 38 that extend from substantially the head 17 to the shank end 28 outside of the mounting bore 11. More particularly, these shank grooves 38 are spaced a slight distance from the diverging shank portion and open at the peripheral locking groove 27. The cuttings and other material will move into and along these shank grooves 38 and fall into the recess 26 outwardly of the block bore 11 and fall free laterally of and axially along the bit shank 28. These shank grooves 38 also reduce the wear contact between the bit shank 16 and the block wall defining the bore 11, thereby reducing friction to enable the bit shank 16 to turn freely and reducing wear on the block 10.

It will be understood that FIGS. 1-4 disclose only one species of the point-attack bit 15 and only one species of the block 10 utilized to mount such a point-attack bit 15. The species of bit 15 can be used with other similar block constructions in order to obtain the same advantageous results. Similarly, the particular species of block 10 can be utilized with other point-attack bits to afford the advantageous results of this bit and block assembly.

For example, FIG. 5 discloses a block 41 provided with a substantially cylindrical bore 42 thereto opening at the front block face 43 and rear block face 44. One end of the bore 42 is provided with outwardly divergent shoulders 45 at the front block face 43. The rear end of the block 41 is provided with an open end counterbore, constituting the recess, which is larger than and communicates with the bore 42.

The locking mechanism disclosed in FIG. 5 is essentially the same as that previously described with respect to the species of FIGS. 1-4, the block 41 includes a rearwardly extending block portion 30 provided with a rear-opening keyhole slot 31. A resilient insert 33 is carried by the block portion 30, the insert 33 being placed into the keyhole slot 31. A locking pin 35 is carried by and extends through the resilient insert 33, the pin 35 including a plate 36 engaging the outer face of the insert 33, and including a pointed, arcuate length head 37 engaging the inner face of the resilient insert 33. The pin head 37 extends into the block counterbore 46.

Obviously, the bit 15 disclosed in FIG. 1 can be utilized in the block 41 of FIG. 5 in exactly the same manner as previously described. However, FIG. 5 discloses another species of bit 47 having a turning means 24 of different construction than that disclosed by the species of bit 15 in FIG. 1.

The bit 47 (FIG. 5) includes an elongate cylindrical shank 50 rotatively mounted in the block bore 42. The shank end 51 extends outwardly of the bore 42 and into the counterbore 46, the block wall defining the counterbore 46 being laterally spaced about and from the periphery of the shank end 51. A peripheral, annular groove 52, is provided in the shank end 51, the pin head 37 in the groove 52 and engaging the shank end 51 to preclude unintentional withdrawal of the shank 50 from the block bore 42.

The bit 47 includes an integral, tapered head 53 formed coaxially with the shank 50. Particularly, the tapered head 53 is substantially conical. The larger portion of the tapered head 53 provides a rearwardly facing annular shoulder 54 engaging the front block 43 around the front opening of the bore 42. The shank 50 is provided with an outwardly diverging shank portion 55 integrally connected to the tapered head 53, the shank portion 55 engaging the outwardly diverging bore shoulder 45. The forward, smaller end of the tapered head 53 is provided with a pointed carbide tip 22.

The turning means 24 consists of a plurality of protuberances 56 extending laterally outward from the periphery of the conical head 53. Although the protuberances 56 in FIG. 5 are shown to be hemispheres, they can be of any shape and can be located in a regular pattern or at random on the periphery and along the length of the conical head 53. In any event, one or more of these protuberances 56 will provide a turning means engageable with the wall 23 upon picking action of the conical head 53 to effect a turning of the head 53 and the shank 50.

The bit shank 50 is provided with a shank portion 48 adjacent the frusto-conical portion 55 which is substantially cylindrical and has a dimension conforming closely to the bore diameter in order to provide substantially full circumferential bearing contact in order to absorb the force placed on the bit 47 by the picking action. The remaining length of the shank 50 is relatively reduced to provide a definite space with the bore wall to permit free passage of cuttings and material axially along the shank 50. This reduced shank portion is provided with a plurality of small protuberances 49 spaced at random or in a predetermined patter circumferentially and axially of the shank 50, such protuberances 49 engaging the block wall defining bore 42. The small protuberances 49 provide a bearing contact, yet do not interfere with the passage of the cuttings in the space between the shank 50 and the bore wall. Moreover, the small protuberances 49 provide for a relatively limited bearing contact area which reduces the friction incurred during rotation of the bit.

It will be understood that the bit 47 can be advantageously utilized with the species of block shown in FIG. 1 in a bit and block assembly to provide all of the functional advantages and results discussed previously.

Specially referring to the embodiment of FIG. 5, the bit 47 is connected to the block 41 by inserting the shank 50 into the block bore 42 until the head shoulder 54 engages the front block face 43. Upon insertion, the tapered shank end 51 will laterally depress the pin head 37 against the loading of the resilient insert 33. Upon complete insertion of the shank 50, the pin head 37 will snap into the annular shank groove 52 and engage the shank to prohibit withdrawal of the shank 50 from the blockbore 42.

As the bit head 53 is moved into a wall 23 in a picking action with the smaller end foremost, the carbide tip 22 and the conical head 53 will enter into the wall to cut, scrape and dislodge the material comprising such wall. The protuberances 56 constituting the turning means 24 engage the wall 23 and cause the conical head 53 to turn or twist in one direction or the other. Upon continuous picking action and movement of the tapered head 53, the head moves through and out of the wall 23. Because the bit head 53 has been turned during this picking action, the head 53 is located in a different relative position for the next picking action into wall 23. The periphery of the head 53 and the carbide tip 22 is constantly being changed in its angular position because of such bit turning, and consequently, during this inten'nittent picking action of the bit head 53, there is a tendency for the head 53 and tip 22 to wear evenly about such periphery and be selfsharpened.

During the turning of bit shank 50 in the block bore 42, the pin head 37 rides in the annular shank groove 52. It is possible for very fine cuttings to enter the block bore 42 between the shank 50 and block 411. The turning action of the shank 50 prevents these fine cuttings from packing within the bore 42 such as to hinder or block the block rotation. These cuttings will pass axially along the bore 42 and bit shank 50, and will fall or be discharged into the large counterbore 46 around the shank end 51, and hence will fall free of the block 10. The pin head 37 will urge these cuttings axially, rearwardly and outwardly of the groove 52 as permitted by the considerable space provided by the enlarged counterbore 46.

To remove the bit shank 47, the bit 47 is forcefully pushed, struck or pried outwardly to remove the shank 50 from block bore 42. Upon this intentional withdrawal, the bit shank 50 will depress the pin head 37 laterally and/or rearwardly against the loading of the resilient insert 33 sufficient to remove the pin head 37 from the annular shank groove 52.

FIG. 6 illustrates another embodiment in which the block 57 is provided with a bore 60 of substantially constant diameter extending therethrough. The rear shank end 61 is tapered axially rearwardly so as to provide the recess62 laterally about this shank end 611. The shank groove 63 is formed in the shank end 61 at a distance spaced axially from the start of the shank taper or where the shank dimension is compatible with that of the bore 60. The locking means is a pin that extends through the block 57 and into the annular groove 63 at one side of the bit shank end 61. The pin 64 holds the bit shank 65 in place, yet permits rotation in the same manner as the assemblies of FIGS. 1-4 and FIG. 5.

The cuttings and other materials moving through the bore are discharged into the recess 62 laterally about the shank end 61 and fall free of the block 57. In this respect, the recess 62 is similar to and performs the function of the recess 26 and counterbore 46 of the embodiments of FIGS. 1-4 and FIG. 5 respectively.

I claim as my invention:

1. A bit and block assembly, comprising:

a. a block provided with a substantially cylindrical mounting bore extending through the block,

b. a bit including:

1. an elongate shank rotatively mounted in the mounting bore, the bit shank being provided with an end extending through and beyond the mounting bore, and laterally clear of the block, and

2. a head having means adapted to strike a wall to turn the bit upon picking of the wall by the head,

c. the block being provided with a portion extending laterally, yet spaced from the shank end, and

d. locking means carried by the lateral block portion and engaging the shank end to preclude unintentional withdrawal of the shank from the mounting bore, yet enable turning of the shank,

e. the mounting bore and the shank being compatibly configurated to provide bearing means spaced to provide passage means, the passage means extending lengthwise of the shank from substantially adjacent the head to the end of the mounting bore to move cuttings through the mounting bore and out of the block and to fall free axially of the shank end.

2. A bit and block assembly as defined in claim l, in which:

f. the shank end is provided with a peripheral groove, and

g. the lock means includes a locking element riding in the groove, the groove and locking element being spaced from the mounting bore axially of 'the shank to prevent blockage of the mounting bore when the shank is mounted in the mounting bore.

3. A bit and block assembly as defined in claim 2, in which:

h. the locking element is resiliently mounted to the lateral block portion,

i. the peripheral groove is annular about the shank and includes a sloping margin, and

j. the locking element includes a substantially pointed tip with an arcuate length riding in the annular groove said locking element being laterally displaceable by said sloping margin.

4. A bit and block assembly as defined in claim 2, in which:

h. the block is provided with an open end counterbore larger than and communicating with the said mounting bore, and

i. the shank end, including the peripheral groove, extends into the counterbore, the counterbore providing a peripheral, lateral space about the shank end and groove.

5. A bit and block assembly, comprising:

a. a block provided with a substantially cylindrical bore extending through the block,

b. A bit including:

1. an elongate shank rotatively mounted in the block bore, the bit shank being provided with an end extending through and beyond the mounting bore, and laterally clear of the block,

2. a head having means adapted to strike a wall to turn the bit upon picking of the wall by the head, and

3. the bit shank being provided with a plurality of circumferential spaced, longitudinal grooves extending from substantially adjacent the head to the shank end outside of the mounting bore for the passage of material axially along the shank and out of the block,

c. the block being provided with a portion extending laterally, yet spaced from the shank end, and

d. locking means carried by the lateral block portion and engaging the shank end to preclude unintentional withdrawal of the shank from the bore, yet enable turning of the shank,

e. the lateral block portion protecting the locking means while the lateral space peripherally about the shank end enables cuttings to move through the bore and out of the block and to fall free axially of the shank end.

6. A bit and block assembly as defined in claim 5, in which:

f. the shank end is provided with a peripheral groove,

g. the locking means includes a locking element riding in the groove, the groove and locking element being spaced from the block axially of the shank to prevent blockage of the bore when the shank is mounted in the bore, and

h. h shank grooves extend along the shank end and open in the eripheral locking groove.

7. A bit and block assembly, comprising:

a. a block provided with a substantially cylindrical bore extending through the block,

b. a bit including:

1. an elongate shank rotatively mounted in the block bore, and

2. a head having means adapted to strike a wall to turn the bit upon picking of the wall by the head,

c. the bit shank includes a reduced end provided with a peripheral groove, the reduced shank end and groove being laterally spaced from the block defining the bore, and

d. locking means carried by the block and engaging the reduced shank end in the groove to preclude unintentional withdrawal of the shank from the bore, yet enable turning of the shank,

e. the block laterally of the reduced shank end protecting the locking means while the lateral space peripherally about the shank end enables cuttings to move through the bore and out of the block and to fall free axially of the shank end.

8. A bit and block assembly as defined in claim 7, in which:

f. the reduced end is tapered,

g. the peripheral groove is spaced axially along the shank end from the start of the taper where the shank dimension is compatible with that of the bore, and

h. the bore and the shank are compatibly configurated to provide bearing means spaced to provide passage means, the passage means extending lengthwise of the shank from substantially adjacent the head rearwardly along the mounted length of the shank.

9. A bit and block assembly, comprising:

a. a block provided with a substantially cylindrical bore extending through the block,

b. a bit including:

1. an elongate shank rotatively mounted in the block bore, and

2. a head having means adapted to strike a wall to turn the bit upon picking of the wall by the head,

3, the bit shank being provided with a plurality of protuberances spaced about the circumference of the bit shank along its length, the the protuberances engaging the block wall to provide a bearing surface and to provide a space between the bit shank and bore wall for the passage of material axially along the shank and out of the block,

c. the bit shank includes a tapered end provided with a peripheral groove, the tapered shank end and groove being laterally spaced from the block defining the bore, and

d. locking means carried by the block and engaging the tapered shank end in the groove to preclude unintentional withdrawal of the shank from the bore, yet enable turning of the shank,

e. the block laterally of the tapered shank end protecting the locking means while the lateral space peripherally about the shank end enables cuttings to move through the bore and out of the block and to fall free axially of the shank end.

10. A bit and block assembly, comprising:

a. a block provided with a substantially cylindrical mounting bore extending through the block,

b. a bit including:

1. an elongate shank rotatively mounted in the mounting bore,

2. a head having means adapted to strike a wall to turn the hit upon picking of the wall by the head, and

c. locking means carried by the block and engaging the shank to preclude unintentional withdrawal of the shank from the bore, get enable turning of the shank, d. the mounting ore and the shank being compatibly configurated to provide bearing means spaced to provide passage means, the passage means extending lengthwise of the shank from substantially adjacent the head to the end of the mounting bore to move cuttings through the mounting bore and out of the block and to fall free axially of the shank end.

11. A bit and block assembly as defined in claim 10, in

which:

e. the shank includes a forwardly disposed substantially continuous bearing portion and a rearwardly disposed intermittent bearing portion providing the lengthwise passage means. 

1. A bit and block assembly, comprising: a. a block provided with a substantially cylindrical mounting bore extending through the block, b. a bit including:
 1. an elongate shank rotatively mounted in the mounting bore, the bit shank being provided with an end extending through and beyond the mounting bore, and laterally clear of the block, and
 2. a head having means adapted to strike a wall to turn the bit upon picking of the wall by the head, c. the block being provided with a portion extending laterally, yet spaced from the shank end, and d. locking means carried by the lateral block portion and engaging the shank end to preclude unintentional withdrawal of the shank from the mounting bore, yet enable turning of the shank, e. the mounting bore and the shank being compatibly configurated to provide bearing means spaced to provide passage means, the passage means extending lengthwise of the shank from substantially adjacent the head to the end of tHe mounting bore to move cuttings through the mounting bore and out of the block and to fall free axially of the shank end.
 2. a head having means adapted to strike a wall to turn the bit upon picking of the wall by the head, c. the block being provided with a portion extending laterally, yet spaced from the shank end, and d. locking means carried by the lateral block portion and engaging the shank end to preclude unintentional withdrawal of the shank from the mounting bore, yet enable turning of the shank, e. the mounting bore and the shank being compatibly configurated to provide bearing means spaced to provide passage means, the passage means extending lengthwise of the shank from substantially adjacent the head to the end of tHe mounting bore to move cuttings through the mounting bore and out of the block and to fall free axially of the shank end.
 2. A bit and block assembly as defined in claim 1, in which: f. the shank end is provided with a peripheral groove, and g. the lock means includes a locking element riding in the groove, the groove and locking element being spaced from the mounting bore axially of the shank to prevent blockage of the mounting bore when the shank is mounted in the mounting bore.
 2. a head having means adapted to strike a wall to turn the bit upon picking of the wall by the head, and
 2. a head having means adapted to strike a wall to turn the bit upon picking of the wall by the head, c. the bit shank includes a reduced end provided with a peripheral groove, the reduced shank end and groove being laterally spaced from the block defining the bore, and d. locking means carried by the block and engaging the reduced shank end in the groove to preclude unintentional withdrawal of the shank from the bore, yet enable turning of the shank, e. the block laterally of the reduced shank end protecting the locking means while the lateral space peripherally about the shank end enables cuttings to move through the bore and out of the block and to fall free axially of the shank end.
 2. a head having means adapted to strike a wall to turn the bit upon picking of the wall by the head,
 2. a head having means adapted to strike a wall to turn the bit upon picking of the wall by the head, and c. locking means carried by the block and engaging the shank to preclude unintentional withdrawal of the shank from the bore, yet enable turning of the shank, d. the mounting bore and the shank being compatibly configurated to provide bearing means spaced to provide passage means, the passage means extending lengthwise of the shank from substantially adjacent the head to the end of the mounting bore to move cuttings through the mounting bore and out of the block and to fall free axially of the shank end.
 3. the bit shank being provided with a plurality of protuberances spaced about the circumference of the bit shank along its length, the the protuberances engaging the block wall to provide a bearing surface and to provide a space between the bit shank and bore wall for the passage of material axially along the shank and out of the block, c. the bit shank includes a tapered end provided with a peripheral groove, the tapered shank end and groove being laterally spaced from the block defining the bore, and d. locking means carried by the block and engaging the tapered shank end in the groove to preclude unintentional withdrawal of the shank from the bore, yet enable turning of the shank, e. the block laterally of the tapered shank end protecting the locking means while the lateral space peripherally about the shank end enables cuttings to move through the bore and out of the block and to fall free axially of the shank end.
 3. the bit shank being provided with a plurality of circumferential spaced, longitudinal grooves extending from substantially adjacent the head to the shank end outside of the mounting bore for the passage of material axially along the shank and out of the block, c. the block being provided with a portion extending laterally, yet spaced from the shank end, and d. locking means carried by the lateral block portion and engaging the shank end to preclude unintentional withdrawal of the shank from the bore, yet enable turning of the shank, e. the lateral block portion protecting the locking means while the lateral space peripherally about the shank end enables cuttings to move through the bore and out of the block and to fall free axially of the shank end.
 3. A bit and block assembly as defined in claim 2, in which: h. the locking element is resiliently mounted to the lateral block portion, i. the peripheral groove is annular about the shank and includes a sloping margin, and j. the locking element includes a substantially pointed tip with an arcuate length riding in the annular groove said locking element being laterally displaceable by said sloping margin.
 4. A bit and block assembly as defined in claim 2, in which: h. the block is provided with an open end counterbore larger than and communicating with the said mounting bore, and i. the shank end, including the peripheral groove, extends into the counterbore, the counterbore providing a peripheral, lateral space about the shank end and groove.
 5. A bit and block assembly, comprising: a. a block provided with a substantially cylindrical bore extending through the block, b. A bit including:
 6. A bit and block assembly as defined in claim 5, in which: f. the shank end is provided with a peripheral groove, g. the locking means includes a locking element riding in the groove, the groove and locking element being spaced from the block axially of the shank to prevent blockage of the bore when the shank is mounted in the bore, and h. the shank grooves extend along the shank end and open in the peripheral locking groove.
 7. A bit and block assembly, comprising: a. a block provided with a substantially cylindrical bore extending through the block, b. a bit including:
 8. A bit and block assembly as defined in claim 7, in which: f. the reduced end is taPered, g. the peripheral groove is spaced axially along the shank end from the start of the taper where the shank dimension is compatible with that of the bore, and h. the bore and the shank are compatibly configurated to provide bearing means spaced to provide passage means, the passage means extending lengthwise of the shank from substantially adjacent the head rearwardly along the mounted length of the shank.
 9. A bit and block assembly, comprising: a. a block provided with a substantially cylindrical bore extending through the block, b. a bit including:
 10. A bit and block assembly, comprising: a. a block provided with a substantially cylindrical mounting bore extending through the block, b. a bit including:
 11. A bit and block assembly as defined in claim 10, in which: e. the shank includes a forwardly disposed substantially continuous bearing portion and a rearwardly disposed intermittent bearing portion providing the lengthwise passage means. 